The role of extrinsic factors in the regulation of periodic population dynamics in small mammals
小型哺乳动物种群周期性波动的外因调节假说

This paper reviewed the new progress in the theory and hypothesis of population regulation in small mammals, focusing on the food hypothesis, predation hypothesis and multi-factorial hypothesis. The food hypothesis includes the role of food quantity, food quality and plant secondary compound in the regulation of population dynamics. In some species that lived in extreme environments, food might be a regulatory factor of the periodic population dynamics. However, food may very likely act as a limiting factor for most small mammals. The predation hypothesis has been considered to be a hopeful hypothesis for explaining the population cycles of some small mammals,with a particular emphasis on some voles and lemmings in the Scandinavian region. The predation hypothesis states that the direct and/or indirect effects of specialist predators on reproductive and physiological activities of northern arvicoline rodents are the cause of the periodic population fluctuation. There is also some evidence against the predation hypothesis. For the multi-factor hypothesis, some experimental manipulation demonstrated that the independent and additive effects of food availability and predation could cause the population cycles in some small mammals, sometimes combining with climate, interspecific competition, space and/or social behaviors. Though the multi-factor hypothesis has been considered as a most promising approach to study the population cycles of small mammals, due to logistic difficulties in the field and excessive expenditure, there is still not enough evidence to support this hypothesis. Additionally, it is difficult to identify the dominant factor(s) that could cause the periodic population fluctuations of small mammals. In spite of these difficulties, the multi-factor hypothesis should be an effective and reasonable way to solve the enigma. At last, we made some suggestions on how to advance the research on the population regulation of small mammals in China.